Problem: $-\dfrac{6}{12} - \dfrac{3}{5} = {?}$
Answer: $ = - {\dfrac{6 \times 5}{12 \times 5}} - {\dfrac{3 \times 12}{5 \times 12}} $ $ = - {\dfrac{30}{60}} - {\dfrac{36}{60}} $ $ = - \dfrac{{30} - {36}}{60} $ $ = -\dfrac{66}{60}$